u-boot-users-admin@lists.sourceforge.net wrote on 07.01.2005 10:32:42:
Hi, I designed an MPC5200 with 256MB RAM (4 x 512Mb chips; MT48LC32M16A2, 8x16bitx4banks). When I force U-boot to just use the first 128 MB, everything is ok (I force the return value from the routine exploring the RAM size). If I try to use the full 256 MB it crashes in the relocation phase (not always at the same point). I'm quite sure the RAM is working, as a test RAM program, residing in the low RAM and testing the full memory from 0x08000000 to 0x0fffffff, always gives result ok (it's started from U-boot running in low memory). I'm using u-boot 1.1.1
Are you using one or two CS signals for your SDRAM ?
If you are using two CS signals, then perhaps you are seeing the effect of MPC5200 errata ID 342, which says: "There is problem when executing code from CS0 that writes data to CS1 of the SDRRAM, and vice versa. As a result, exception 700 will be forced."
We had designed an MPC5200 board that used CS0 and CS1 for SDRAM. Having read this we changed our board design to use just CS0 for SDRAM. I was having a problem with getting u-boot to work with the upper half of the memory space, but I never really found out the exact cause. We simply decided that we could not use two CS because of this errata. After we changed to using just CS0, we have experience no problems with this.
Regards, Jon Benediktsson Marel hf.